diff --git a/UsbDk/WdfDevice.cpp b/UsbDk/WdfDevice.cpp
index ce13b78..314f0fb 100644
--- a/UsbDk/WdfDevice.cpp
+++ b/UsbDk/WdfDevice.cpp
@@ -60,7 +60,7 @@ PWDFDEVICE_INIT CPreAllocatedDeviceInit::Detach()
 
 NTSTATUS CPreAllocatedDeviceInit::SetPreprocessCallback(PFN_WDFDEVICE_WDM_IRP_PREPROCESS Callback,
                                                         UCHAR MajorFunction,
-                                                        PUCHAR MinorFunctions,
+                                                        const PUCHAR MinorFunctions,
                                                         ULONG NumMinorFunctions)
 {
     auto status = WdfDeviceInitAssignWdmIrpPreprocessCallback(m_DeviceInit,
diff --git a/UsbDk/WdfDevice.h b/UsbDk/WdfDevice.h
index c2fd230..96ca238 100644
--- a/UsbDk/WdfDevice.h
+++ b/UsbDk/WdfDevice.h
@@ -36,7 +36,7 @@ public:
 
     NTSTATUS CPreAllocatedDeviceInit::SetPreprocessCallback(PFN_WDFDEVICE_WDM_IRP_PREPROCESS Callback,
                                                             UCHAR MajorFunction,
-                                                            PUCHAR MinorFunctions,
+                                                            const PUCHAR MinorFunctions,
                                                             ULONG NumMinorFunctions);
 
     NTSTATUS SetPreprocessCallback(PFN_WDFDEVICE_WDM_IRP_PREPROCESS Callback, UCHAR MajorFunction, UCHAR MinorFunction)